This invention is directed to the formation of inflatable members and particularly to inflatable balloons for dilatation catheters used in angioplasty procedures, commonly referred to as percutaneous transluminal coronary angioplasty (PTCA).
In a typical PTCA procedure a dilatation balloon catheter is advanced over a guidewire to a desired location within the patient's coronary anatomy where the balloon of the dilatation catheter is properly positioned within the stenosis to be dilated. The balloon is then inflated to a predetermined size with radiopaque liquid at relatively high pressures which can generally range from 4-20 atmospheres to dilate the stenosed region of the diseased artery. One or more inflations may be needed to effectively dilate the stenosis. The catheter may then be withdrawn from the stenosis or advanced further into the patient's coronary anatomy to dilate additional stenoses.
The catheters used to insert stents into a patient's blood vessel are very similar to the catheters employed for angioplasty. The stent is mounted onto the balloon of the catheter in a contracted or otherwise unexpanded state, the catheter with the stent is advanced through the patient's vasculature until the balloon and stent thereon are disposed within a desired region of the patient's vasculature, such as a coronary artery. The balloon is inflated to expand the stent into position within the desired region of the patient's blood vessel.
Presently used balloons are formed of a polymer such as polyethylene terephthalate (PET), polyethylene (PE), nylon and the like. The strength requirements for balloons whether for dilatation and stent delivery has tended to increase over the years. But it has become more difficult with conventional manufacturing procedures to form high strength balloons with thin walls of uniform thicknesses without pin holes. Typical procedures involve blowing of a tubular parison, usually within a mold having an interior surface corresponding to the desired inflated shape of the balloon.
Dilatation balloons of non-standard shapes, such as bifurcated balloons shown in U.S. Pat. No. 4,456,000, are difficult to manufacture without seams, flow lines, flash or other defects. What has been needed and heretofore unavailable is a method of forming balloons having high strength, thin walls and low incidence of pin holes and in a variety of shapes and sizes without the prior defects. The present invention satisfies these and other needs.